Yeah, I think it's a combination of bad luck, lots of junk on Manhattan streets, and small wheels. It's not a big deal; you get a flat, you fix it, you go on. I order new tires long before I need them.

I am totally amazed when I hear about the people who go for years without a single flat. In fact, I have to stop myself from saying something crass like "did you ever ride your bike, in this time?" Flat tires happen. It's part of cycling.